Fine fiber electro-spinning equipment, filter media systems and methods

The present invention generally relates to electrostatic spinning of fine fibers from a polymeric solution in an electrostatic field created by a voltage differential between a spinning electrode and a collecting electrode and more particularly relates to a new spinning electrode equipment arrangement and/or electro-spinning methods. Other aspects of the invention may also relate to filter media production systems and methods, that is application of fine fibers to filter media so as to create a high efficiency layer upon the filtration media for filtering contaminants out of a fluid stream.

The production of fine fibers from polymeric solution through electrostatic spinning (a.k.a. “electro-spinning”) via an electric field created by a voltage differential between a collecting electrode and a spinning electrode is known. For example, as shown in U.S. Pat. No. 6,743,273, polymeric solution is pumped to a spinning electrode in the form of a rotating emitter in which the pump solution is pumped from a reservoir and forced through holes in the emitter. Upon exiting, the electrostatic potential between a grid and the emitter imparts a charge which causes the liquid to be “spun” as thin fine fibers where they are collected on a substrate as an efficiency layer. During this process, the solvent is evaporated off the fine fibers which draws down the fiber diameter during their flight.

Another example of an electrostatic spinning device is shown in Patent Publication Nos. US2006/0290031 and WO2006/131081. The spinning electrode designs disclosed in these applications are in the form of a rotating drum-like body that may take several different forms. The drum is situated and bathed within a polymeric solution reservoir and is rotated about an axis perpendicular relative to the path of a collection media. By rotating the drum through the polymer solution, the spinning surface of the charged electrode is coated with the polymeric solution. Various drum like body variations are shown throughout these two patent publications to include providing a multiple pointed tips to create discrete spinning locations where fine fibers are generated.

The present invention provides for improvements over the existing state of the art as it relates to electrostatic fine fiber production and spinning electrode design and/or in relation to the production of fine fiber filtration media.

The present invention has several aspects that may be claimed and stand as patentable individually or in combination including but not limited to the following.

A first aspect of the present invention is directed toward an apparatus for production of fine fibers onto a suitable collection media. The apparatus includes two electrodes which are spaced apart in which the spinning electrode includes a strand that is entrained upon at least two guides. The apparatus has an entrance region and an exit region that are spaced apart along a first path such that the collection media is adapted to be driven along the first path from the entrance region to the exit region in spaced relation from the spinning electrode. A drive unit is adapted to drive the strand along the at least two guides for movement along a second path that is transverse to the first path (e.g. crosswise and may be perpendicular according to certain embodiments). A voltage source is arranged to generate a voltage differential between the first and second electrodes for generating an electrostatic field for the spinning of fine fibers.

The strand may take the form of a chain, band, strip or other strand structure. According to a preferred embodiment, the strand can take the form of an endless strand that is driven about an endless continuous path. The second path mentioned above is a part of this endless path. The endless path further includes a return path in spaced relation with the endless strand that is further away from the collecting electrode along the return path as compared with the second path where electrospinning of fine fibers occur. Additionally, according to certain embodiments, a dipping basin is provided which is adapted to contain a suitable polymer solution. The endless strand along the return path runs through the dipping basin for dipping into the polymer solution and thereby coats the endless strand with the polymer solution.

Another aspect of the present invention is directed toward a filter media production system. The system includes a roll of substrate material that supplies a sheet of substrate material along a first path through an entrance region to an exit region of fine fiber generation machine. The sheet has opposed side edges generally parallel to the first path. The fine fiber generation machine includes at least one strand and a drive unit driving the strand along a second path from a first guide to a second guide that is transverse relative to the first path. The strand is wetted with a polymer solution and subject to a voltage differential to provide an electrostatic field for generating fine fibers that are subsequently deposited upon the substrate material.

According to certain embodiments, such an aspect may also involve an endless strand which is run along an endless path and may also relate to dipping a portion of the endless strand at any one given time within a basin of polymer solution to replenish the coating of polymer solution upon the endless strand.

Another inventive aspect includes an apparatus for the production of fine fibers onto a collection media, wherein at least one spinning electrode has a linear segment maintained at a constant spacing relative to a planar collection electrode. According to this aspect, a collection electrode has a planar support surface for supporting the collection media, at least one spinning electrode has a linear segment adjacent the planar support surface and a drive unit drives the spinning electrode, while maintaining a constant spacing between the linear segment and the planar support surface when driven by the drive unit. A voltage source is arranged to generate a voltage differential between the first and second electrodes for generating the spinning of fine fibers.